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A Zn-Al layered double hydroxide (LDH) conversion coating was investigated as a surface treatment for galvanized steel. Zn-Al LDH crystals were grown in situ on the galvanized steel surface in room temperature at different periods. Grazing Incidence Xray Diffraction verified the formation of Zn-Al LDH flakes on the surface. Scanning Electron Microscopy showed that Zn-Al LDH flakes were evenly distributed as a continuous coating on the surface of galvanized steel. Roughness and surface free energy of the coatings were evaluated by Atomic Force Microscopy and contact angle measurements. Corrosion propensity of the LDH coatings was analyzed utilizing Electrochemical Impedance Spectroscopy (EIS) and polarization. A 6 times increase in impedance at 0.01 Hz and 10 times decrease in corrosion current density was achieved for galvanized steel by LDH conversion coating in best practice. To assess the role of the LDH conversion coatings on adhesion strength and corrosion resistance of overlying organic coatings, epoxy coating was applied on LDH conversion coated surfaces and tested by pull-off, salt spray and EIS. Results signified 23 times increase in impedance at 0.01 Hz and 80% decrease in adhesion loss for organically coated galvanized steel after LDH treatment at optimal condition. [ABSTRACT FROM AUTHOR]

In the present work, the synergistic effect of diethyldithiocarbamate (DDTC) molecules and Ce3+ cations on the corrosion inhibition of the 2024-T3 aluminum alloy was assessed by employing surface analysis and electrochemical tests. For this purpose, potentiodynamic polarization, and electrochemical impedance spectroscopy were measured in the presence of Ce3+ cations and DDTC molecules. Also, surface analysis methods were employed to study the mechanisms of the inhibition in the presence of the Ce3+ cations and DDTC molecules. The results showed strong synergism between the DDTC molecules and Ce3+ cations due to the creation of a complex film on the surface of AA2024-T3. The complex film formation on the AA2024-T3 surface was proved using scanning electron microscopy, X-ray photoelectron spectroscopy, and attenuated total reflection Fourier-transform infrared spectroscopy. Also, cathodic inhibition behavior and a wide passivation range attributed to the Ce+ DDTC system were illustrated by the potentio dynamic polarization testing. [ABSTRACT FROM AUTHOR]

In this study, combinations of two environmentally friendly compounds including a silane-based organic-inorganic coating and a rare earth (RE) salt have been investigated for mitigation of corrosion activity of mild steel. Bilayer silane coatings based on methyl triethoxy silane (MTES) and tetraethyl orthosilicate (TEOS) were reinforced by different amounts of praseodymium cations (Pr3+). The effects of Pr loading on the hydrophobicity and surface properties of the coating were studied by contact angle measurements. Fourier Transform Infrared (FT-IR) spectroscopy was done to scrutinize the curing process and possible structural changes of silane network in the presence of inhibitor. Despite the decrease in the hydrophobic nature of silane coating, the Pr cations did not change the curing of the coating. Electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) measurements confirmed the high corrosion inhibition power for the mild steel sample immersed in 400 ppm Pr containing the saline solution. The results of EIS, polarization and salt spray tests besides the scanning electron microscopy (SEM) images confirmed the silane coating healing ability and corrosion protection properties enhancement in the presence of Pr cations. [ABSTRACT FROM AUTHOR]